Polycarbonate resin is known as a resin which has the best impact resistance among engineering plastics and a good heat distortion resistance, and by making use of these advantages, it has been applied to various fields.
However, polycarbonate resin has disadvantages such as poor solvent-resistance and flow property in molding processing. For example, if polycarbonate resin comes into contact with various organic solvents, gasoline or the like, cracking may happen in the surface of its molded articles, or the molded articles may be dissolved Particularly, when forming aromatic polycarbonate resins by injection molding or the like, relatively high injection speed and pressure are required. Consequently, some strain may remain in the molded articles by which serious cracks generate in this strained portion Moreover, in addition to the resistance against gasoline, engine oil or the like which has hitherto been required, a resistance against mixed solvents (e.g. wax remover) has become to be further required.
On the other hand, polyethylene terephthalate resin has excellent solvent-resistance and flow property in molding.
Accordingly, for the purpose of improving the disadvantages of polycarbonate resin, various resin compositions have been studied and reported. For example, Japanese Examined Patent Publication No. 36-14035, Japanese Examined Patent Publication No. 39-20434, Japanese Unexamined Patent Publication No. 59-176345, Japanese Examined Patent Publication No. 5-87540, Japanese Unexamined Patent Publication No. 3-140359 and Japanese Unexamined Patent Publication No. 4-85360 propose resin compositions composed of a polycarbonate resin and a polyester resin and those to which a polyolefin or a rubber component is further added, and disclose that some improvement of solvent-resistance is obtained.
Also, in Japanese Examined Patent Publication No. 58-13588, Japanese Unexamined Patent Publication No. 62-48760 and Japanese Unexamined Patent Publication No. 62-48761, it is disclosed that by blending a polycarbonate resin, a polyester resin and an ethylene-ethyl acrylate copolymer in a specific ratio, resin compositions having excellent moldability, heat stability, impact resistance and heat resistance are obtained.
Recently, by the reason that cost reduction has been strongly demanded in various applied fields of polycarbonate resin, abolition of plating, coating and the like has been studied as for the molded articles used as automobile exterior materials. The plating or coating of the molded articles has been made not only for the better appearance but also for forming a protective film Therefore, omission of plating or coating results in direct contact of the molded articles with solvents. Accordingly, the required level of solvent-resistance now has become much higher than that of before.
Also, reduction of the number of component parts is required for the cost reduction Consequently, the component parts are united to one unit and incidentally the shape becomes more complicated and bigger. A better molding processability adaptable to formation of such shaped articles, in other words, both a better heat stability and a better flow property in molding, have become to be required.
However, in the case of only using the above-mentioned resin compositions composed of polycarbonate resin and polyester resin or those further containing polyolefin or rubbery component, the solvent-resistance does not reach a level which enables to use as a material for automobile exterior parts without coating or plating, and also, the heat stability and flow property in molding are not so high as to meet the use for recent automobile exterior parts.
The above-mentioned compositions composed of polycarbonate resin, polyester resin and ethylene-ethyl acrylate copolymer are also not sufficient for a recent high level requirement of solvent-resistance. So further improvement is desired.
As aforementioned, in prior art, polycarbonate resin compositions having an excellent solvent-resistance which is applicable to automobile exterior use without coating or plating, and having excellent flow property in molding and heat stability which are adaptable to molding into more complicated and bigger shapes, have not been obtained yet.